Field of the Invention
Embodiments of the present invention generally relate to a substrate support bushing. More particularly, embodiments of the present invention relate to a substrate support bushing for use with a lift pin in substrate support pedestal.
Description of the Related Art
Thin film transistors have been made on large glass substrates or plates for use in monitors, flat panel displays, solar cells, personal digital assistants (PDA), cell phones, and the like. These transistors are made by sequential deposition of various films including amorphous silicon, both doped and undoped silicon oxides, silicon nitride, and the like in vacuum chambers. The film deposition takes place in a deposition chamber. Within each deposition chamber, the substrate being processed typically rests on a support pedestal situated within the chamber. To facilitate transfer of the substrate between different deposition chambers, support members, such as a plurality of lift pins for example, are extendable through an upper surface of the support pedestal so that the substrate is spaced apart from the support pedestal. This allows a transfer mechanism, such as a robot blade, to slide underneath a back side of the substrate and lift the substrate off the support pedestal without causing damage to either the support pedestal or the substrate.
In conventional deposition chambers, the lift pins are usually housed in a bushing disposed in the support pedestal and have a tendency to bend or tilt in the bushing after repetitive loading and unloading of the substrates. Film deposition may also inadvertently occur on the inside of the bushing since the bushing is exposed to process gasses used during processing of the substrate. The inadvertent film deposited inside the bushing may cause the lift pins to choke during the loading and unloading movement, and damage or break the lift pins. Accordingly, the lift pins are and bushings must be regularly replaced after periods of use, causing down time for removing the damaged pins and installing the replacements.
Therefore, there is a need for a method and apparatus that increases the longevity of bushings and lift pins.